EXPRESSION OF A PUTATIVE PRECURSOR MESSENGER-RNA FOR SPERM-ACTIVATINGPEPTIDE-I IN ACCESSORY CELLS OF THE OVARY IN THE SEA-URCHIN HEMICENTROTUS-PULCHERRIMUS

A cDNA clone encoding egg-jelly peptide, SAP-I (Gly-Phe-Asp-Leu-Asn-Gl y-Gly-Gly-Val-Gly), was isolated from a Hemicentrotus pulcherrimus ova ry cDNA library and its nucleotide sequence was determined. The cDNA w as 1282 bp long and an open reading frame predicted a protein of 334 a mino acids containing 5 SAP-I and 7 SAP-I-like decapeptides, each sepa rated by a single lysine residue. The cDNA hybridized to two species o f mRNA (1.3 kb and 2.0 kb) from H. pulcherrimus ovaries. Northern blot analysis showed that the 1.3 kb transcripts appeared in ovaries colle cted from November to April and the 2.0 kb transcripts were detected o nly in ovaries collected in January. An expression study of the SAP-I precursor gene, by in situ hybridization with a non-radioactive RNA pr obe synthesized using the 1.3 kb cDNA as template, demonstrated that a bundant SAP-I precursor transcripts were expressed in the accessory ce lls, but not in the growing oocytes.